Siemens SINUMERIK 840D sl Function Manual page 191

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The process quantity, e.g. hydraulic pressure, is switched using a standard valve

that is controlled in a safety–related fashion. A pressure sensor signals the status

of the process quantity. If the valve can no longer switch due to a fault condition,

then using a safely controlled standard contactor, the motor that is generating the

pressure, is shutdown. The advantage of this particular version is that components

can be used that are already available as standard. As to whether this solution can

be used, must be confirmed as a result of the risk assessment (see Fig. 7-4).

High Feature

When OK, only the valve is

remains powered–up.

In the case of a fault, the

feedback signal from the

received, the pump motor is

additionally switched.

Cascaded shutdown using fail–safe outputs

In other cases a second actuator must be connected in series in the load circuit

(see Fig. 7-5).

In conjunction with the safety–related control of a brake, no feedback signal is

available. The brake test will identify as to whether the actuator is correctly func-

tioning from a mechanical perspective.

SINUMERIK 840D sl/SINAMICS S120 SINUMERIK Safety Integrated (FBSI sl) – 05.2008 Edition

Connecting Sensors/Actuators

7.1 Safety–related input/output signals

ET 200S PROFIsafe

circuit, valve

circuit, motor

Sinamics s120